J. Am. Chem. SOC. 1993,115, 10097-10103
10097
Preparation and Reactivity of Persistent and Stable Silyl-Substituted Bisketenes Da-chuan Zhao, Annette D. Allen, and Thomas T. Tidwell' Contribution from the Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S I A1 Received May 28, 1993'
Abstract: 2,3-Bis(trimethylsilyl)- 1.3-butadiene- 1,4-dione (1) is formed as the only product on dhermolysis of 3,4-bis(trimethylsilyl)cyclobut-3-ene-l,2-dione (2), and the rate of ring opening of 2 is comparable to that of substituted cyclobutenes and cyclobutenones. Photolysis of 2 also forms 1, which reacts with ethanol in a stepwise fashion with faster addition of one ethanol molecule to give an isolable monoketene 18, which reacts in a further slower step to give succinatediesters, accompanied by desilylation. 2,3-Bis(tert-butyldimethylsilyl)-1,3-butadiene-l,4-dione (3), prepared analogously to 1, similarly adds one molecule of methanol to give the isolable monoketene 20, which then reacts to give dimethyl 2,3-bis(tert-butyldimethylsilyl)succinate (21) as the major product. The reaction of 1 with H2O is faster than with alcohols and forms (E)-and (Z)-2,3-bis(trimethylsilyl)succinic anhydrides (13) as the first observed products. The reactivity of 1 with different nucleophilic solvents is correlated by the Winstein-Grunwald equation and increases with both solvent ionizing power and solvent nucleophilicity.
The preparation in this laboratory of 1, the first stable and persistent 1,3-butadiene-1,4dione, by the thermolysisor photolysis of 3,4-bis(trimethylsilyl)-3-cyclobutene-1,Zdione (2) (eq 1) was
R = MejSi (Z), t-BuMepSi (4), H ( 6 )
prepared, but from the X-ray structure, the geometry of this species was greatly different from the bisketene structure 5.3j There have also been reports of bisketenes such as 7& and 8 where the ketenyl groups are further removed from one another: and in the case of 8,4bthe species is a long-lived solid at room temperature.
R = MqSi (1); t-BuMqSi (3), H (5)
recently reported.' Details of the preparation of 1and its analogue 3 are reported herein, along with studies of their reaction with nucleophilicwater and alcohols,and the properties of intermediate monoketenes formed in these reactions. Bisketenes have been sought since the early days of ketene chemistry. Carbon suboxide (O=C=C=C--O) was prepared in 1906 by Diels and Wolf by dehydration of malonic acidZaand in 1908 by Staudinger and Bereza by the bis dehalogenation of C B ~ ~ ( C O B ~ The ) Z . ~extensive ~ chemistry of C3O2 has been Several nonsilylated analogues of 1 have been prepared, usually by photolysis of cyclobutenediones related to 2, and some of these were directly observed at low temperature^,^ including the parent 6.3a,b However in all cases these rapidly reverted to the more stable cyclobutenediones at room temperaturea3 A stable metal-complexed ketene of this type was *Abstract published in Advance ACS Abstracts, October 1, 1993. (l)Zhao, D.-c.; Tidwell, T. T. J . Am. Chem. Soc. 1992, 114, 1098010981. (2) (a) Diels, 0.;Wolf, B. Chem. Ber. 1906,39,689-697. (b) Staudinger, H.; Bereza, S. Chem. Ber. 1908,41,4461-4465. (c) Ulrich, H. Cycloaddition Reactions of Heterocumulenes; Academic Press: New York, 1967; Chapter 3, pp 110-121. (d) Kappe, T.; Ziegler, E. Angew. Chem.,Int. Ed. Engl. 1974, 13,491-504. ( e ) Kappe, T. In Methoden der Organischen Chemie; Thieme: Stuttgart, Germany, 1993; Vol. 15E. (3) (a) Maier, G.; Reisenauer, H. P.; Sayrac, T. Chem. Ber. 1982, 115, 2192-2201. (b) Kasai, M.; Oda, M.; Kitahara, Y. Chem. Lett. 1978,217218. (c) Hochstrasser, R.; Wirz, J. Angew. Chem., Int. Ed. Engl. 1989.28, 181-183. (d) Tomioka,H.; Fukao,H.; Izawa,Y. Bull. Chem.Soc.Jpn. 1978, 51, 540-543. (e) Miller, R. D.; Kirchmeyer, S. J. Org. Chem. 1993, 58, 90-94. ( f ) Obata, N.; Takizawa, T. Bull. Chem. Soc. Jpn. 1977,50,20172020. (g) h a t e , D. R.; Johnson, L. J.; Kwong, P.C.; Lee-Ruff, E.; Scaiano, J. C. J. Am. Chem. Soc. 1990,112,8858-8863. (h) Mosandl, T.; Wentrup, C. J. Org. Chem. 1993, 58, 747-749. (i) Toda, F.; Garratt, P.Chem. Rev. 1992, 92, 1688-1707. u) Jewell, C. F.,Jr.; Liebeskind, L. S.; Williamson, M. J. Am. Chem. Soc. 1985,107,6715-6716.
o=c#==c=o 7
The stability of 1 was anticipated on the basis of ab initio molecular orbital calculation^^^ that indicated that the hydrogensubstituted cyclobutenedione 6 was more stable than the wrresponding anti-planar bisketene 5 by only 6.9 kcal/mol, while the SiH3 group was more stabilizing to a ketene compared to an alkene by 7.6 kcal/m01.~~ If these effects are additive and if the stabilizing effects of the SiH3 and Me& groups are the same, then the anti-planar bisketene 1 would be more stable than 2 by 8.3 kcal/mol. The successful preparation of 1 provides experimental confirmation of this calculation and shows that the effect of the Me3Si group in stabilizing monoketenes5is qualitatively applicable to bisketenes as well. The bisketene structure of 5, is however, calculated to be destabilized relative to ketene and butadiene; thus, the isodesmic reaction of eq 2 has a calculated hE of -1 1.9 kcal/mol, on the basis of the calculatedsa energies of the individual species.5f (4) (a) Hatchard, W. R.; Schneider, A. K. J . Am. Chem. Soc. 1957, 79, 62614263. (b) Blomquist, A. T.; Meinwald, Y. C. J. Am. Chem. Soc. 1957, 79,2021-2022. (c) Blomquist, A. T.; Spencer,R. D. J . Am. Chem. Soc. 1948, 70, 30-33. (d) Baldwin, J. E.J . Org. Chem. 1963, 28, 3112-3114. ( 5 ) (a) Gong, L.; McAllister, M. A,; Tidwell, T. T. J . Am. Chem. Soc. 1991,113,6021-6028. (b) The reaction SiH,CH=C-O + C H d H 2 SiH,CH=CHZ + C H 6 4 has AE = 7.6 kcal/mol. (c) Allen, A. D.; Tidwel1,T. T. TetrahedronLett. 1991,32,847-850. (d) Ruden, R. A. J. Org. Chem. 1974, 39, 3607-3608. (e) Danheiser, R. L.; Sard, H. J. Org. Chem. 1980, 45, 4810-4812. ( f ) Anti-planar structures for 5 and butadiene. (8) Shchukovskaya, L. L.; Pal'chik, R. I.; Lazarev, A. N. Dokl. Akad. Nauk SSSR, 1965,164,357-360. (h) Kita, Y.; Sekihachi,J.; Hayashi, Y.; Da, Y.; Yamamoto, M.; Akai, S . J . Org. Chem. 1990, 55, 1108-1112.
OOO2-7863/93/1515-lO97$04.00/00 1993 American Chemical Society
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10098
Zhao et al.
J. Am. Chem. SOC.,Vol. 115, No. 22, 1993 AE = D 2CHz=C=0+ (CH=CHz)2 -11.9 kcal/mol
(CH=C=O)z + 2CHpCH2
(2)
Table I. Rate Constants for Formation of Bisketenes by Cyclobutenedione Ring Opening io CDCl3 (9' X
104)
6
Results Reaction of bis(trimethylsily1)acetylene with dichloroketene generated by dechlorination using a zinocopper coupleba4gave the dichlorocyclobutenone9 in 88% yield. Simplifiedprocedures involving activation of zinc by ultrasonicationa or dry heatingbe have appeared, and both have subsequently been of usebfin the preparation of 9. The reaction of 96g,b with concentrated H2SO4 at 55 OC gave 2 in 73% yield after chromatography (eq 3).
T ("C) 99.7 99.0 87.8 87.5 81.0 80.0
ki (2) 9.47 9.45 2.6 1 2.52 1.17 1.11
Eaa (kcal/mol) AH*(kcal/mol) hs* (eu)
29.3 t 0.5 28.6 0.5 0.2 f 0.4
ki (4) 7.04 2.86 0.757
T ("C) 87.1 79.4 68.0
**
28.5 0.6 27.8 0.5 3.8 & 1.5
*
ll119.4)
11%) 1555
Preparation of the corresponding bis(fert-butyldimethylsilyl) derivatives 10 and 4 were carried out similarly, except that the hydrolysis of 10 to 4 proved to be less efficient and gave 4 in 44% yield. Heating of 2 or 4 in degassed CDC13 gave complete conversion to 1 and 3, respectively, as the only products detectable by lH NMR. The bisketenes were obtained preparatively by heating samples of 2 or 4 in a N2 atmosphere. Pure 1 was also obtained by injection of 2 into a gas chromatograph and collection of the pure product. The structures of 1 and 3 follow from their lH and 13C NMR spectra,' especially the 13C signals of the carbonyl carbons at 6 18 1.83 and 182.24, respectively, and those of CBat 5.62 and 4.27, respectively. The ketene Me3SiCH=C-O shows the corresponding carbons at 6 179.2 and -0.1, respecti~ely,~~ while those of f - B u M e 2 S i C H 4 4 are at 179.96 and -3.29, re~pectively.~~ Characteristic ketene IR bands are at 2084 cm-' for 1 and 2076 cm-l for 3. These ketenes show broad UV absorptions &(hexane) at 325 (e 250) and 376 (t 110) nm (1) and 326 (t 160) and 400 (t 88) nm (3). Kinetic data for the ring opening of 2 and 4 to 1 and 3, respectively, were obtained by monitoring the change in the 'H NMR spectra and are given in Table I. These lead to Eaa= 29.3 and 28.5 kcal/mol, respectively. The photolyses of 2 and 4 at 350 nm also led to the formation of the bisketenes 1 and 3, accompanied by the formation of the alkynes (eq 4).
q0
hv
RMe Si
1.209 11.199)
Figure 1. Bond angles and bond lengths for 2 - 1 3 and E-13 (in parentheses).
and 12 in isolated yields of 14 and 7%, respectively, along with small amounts of unidentified products (eq 5 ) . 0
_c 02
Me3Si
(6) (a) Danheiser, R. L.; Savariar, S.; Cha, D. D. Org. Synrh. 1989.68, 32-40. (b) Danheiser, R. L.; Sard, H. Tetrahedron Leu. 1983, 24, 23-26. (c) DeprC, J.-P.;Greene, A. E. Org. Synth. 1989,68,41-48. (d) Mehta, G.; Rao, H. S . P.Synrh. Commun.1985,15,991-1000. (e)Stenstr~rm,Y. Synth. Commun. 1992, 22, 2801-2810. (0 Unpublished results of Jihai Ma. (8) Garratt, P. J.; Tsotinis, A. J . Org. Chem. 1990,55,84-88. (h) A compound previously prepared and assigned the structure 9 is now assigned a different unknown structure on the basis of its method of preparation and spectral characteristics (Dr. P . J. Garratt, private communication). (7) (a) Grishin, Yu. K.; Ponomarev, S . V.; Lebedev, S . A. Zh. Urg. Khim. 1974,404-405. (b) Firl, J.; Runge, W. 2.Nururforsch. 1974,29B, 393-398. (c) Valenti, E.;Pericas,M.A.;Serratosa, F.J. Org. Chem. 1990,55,395-397.
0
0
11
12
The reaction of 1 in 1/ 10 H20/acetone for 5 min at 25 'C gave rise to the products 13 and 14 in the relative yields shown of the crude product as observed by lH NMR, including 16% unreacted 1,2% of the oxidation products of 1,and further signals tentatively assignedto the mono trimethylsilylatedderivative from 13. After prolonged reaction with H20, the observed products were 14 and succinic acid. Both 2-13 and E-13 were isolated as crystalline solids, and their structures were established by X-ray crystallography.6 Me3Si ,fox 04C
+
Me3S)$
SiMe3 1
The bisketenes 1 and 3 appear to be stable indefinitely at room temperature in the dark in the absence of air. Bubbling of 0 2 into a solution of 1 in refluxing toluene gave the anhydrides 11
(5)
Me3Si
1
acetone
\c4I
+
Me3si$0
4o 0
Me3Si
2-13(42%)
Me3Siq;
+
